The tip-apex distance is the sum of the distances from the tip of the lag screw to the apex of the femoral head on both the AP and lateral radiographic views

The tip-apex distance is the sum of the distances from the tip of the lag screw to the apex of the femoral head on both the AP and lateral radiographic views. The sum should be
a. 25 mm
b. 20 mm
c. 15 mm
d. 10 mm